Galvanometer having balanced



July 21, 1953 M. E. MoRRow GALVANOMETER HAVING BALANCED COIL ASSEMBLY Filed March 30 1951 INVENTOR.

m/- Ili||||i|| Patented July 21, 1953 t OFFICE GALVAN OMETER HAVING BALANCED COIL ASSEMBLY A Marvin E. Morrow, Tulsa, Okla. Application March 3o, 1951, serial N0.`218,41'1y s-claims. (o1. 324-97) This invention 'has to `do with galvanometers and .particularly with those used in Vseismograph cameras, the primary object being-to improve upon the mounting for the coil thereof to permit perfect balancing of the Acoil both statically and dynamically.

used in seismograph oscillograph cameras conventionally take the form of a spool. The coil is wound about a pair of spaced spools and each spool receives a filament or Vribbon through the bore thereof for suspending the entire'vibratory assembly within a mounting tube therefor.

Thevibrator assemblyis disposed between a pair of magnetic polesra'nd thereby subjected to flux acting upon the coil thereof. Accordingly, sensitivity of the galvanometer depends directly upon the form-and construction of the vibratory assembly thereof. The entire instrument is extremely small and the vibratory assembly is, therefore, difficult to manufacture with the precision necessary to proper performance,

It is themost important object of the present invention to provide a galvanometer vibrator of reduced weight and having means of joining the coil thereof with the suspension ribbons to permit pre-adjustment and setting with absolute balance prior to final assembly and use.

Another object of this invention is to reduce the Ycost of galvanometers through improved steps of manufacture capable of producing accurate balance with minimum workman effort. A further object hereof is to provide a semicylindrical end mounting for'galvanometer coils, each having a at innermost face for receiving its suspension filament, along which face the filament may be adjusted prior to nal attachment to balance the coil perfectly.

Other equally important objects relate to details of construction, all of which will be made clear as the following specification progresses,

reference being had tothe accompanying drawing, wherein:

v'Figure 1 is a longitudinal, sectional View through a galvanometer for seismograph oscillograph cameras embodying the improved balanced coil assembly forming the subject matter of my present invention. l

Fig; 2 is an'enlarged, fragmentary, side elevational view of the coil assembly per se showing the same detached from associated parts of the galvanomete'r, parts being in section to reveal details of construction.

Fig. 3 is a cross-sectional view taken on irregular line III-III of Fig. 2 looking in the direction of the arrows; and

Fig. 4 is aV fragmentary, side elevational view of oneV end of the coil assembly illustrating the manner of adjustment of one of the suspension filaments. Y

Galvanometers for recording oscillographs or camera takeV various forms and one modifica- Y tion such as illustrated in Fig. 1 of thedrawing End mountings for the coil of galvanometers is fully described in my-co-pending application, Serial No.'1'84,156, iiledS'eptember 11, 1950, this being a continuation in partV of said co-pending case. Briefly, galvanometer I shown in Fig. li, `may comprise anelongated tube I2 having apair of 'opposedspaced-apart magnetic poles IllV mounty that the same each comprise a semi-cylindrical A ed therein between which a coil I6 of a vibratory assembly I8 is suspended for oscillatoryfrotation in response to magnetic flux passing between the poles I4. Themeans for suspending the assemblyk I8 within the tube I2 maybe varied and for the present purposes, such -Vmountings may comprise a spring 20 and its Aassociated parts at one end ofthe tube I2 and a head 22 at the opposite endof tube I2.

A -small mirror 24 `is ordinarily carried'v by the vibratory assembly I8 to reflect a light beam upon a moving film (not shown) torecord the oscillations of coil IB as it responds to the pas.- sage of'electrical` currents therethrough. vAccordinglyf, the tube I2 is provided with an open'- ing 2S in alignment with the mirror' 24 and preferably covered by a `transparent `panel 28.

As above indicated', the assembly I8 is ofextremely minute dimensions and it is pointed out that Figs. 2 to 4 inclusive are magnified views of such assembly. Because of such relatively small size it is diicult to properly balance the assembly I8 within the tube I2 so as to rrender the coil I6 insensitive to mechanical vibrations.

In accordance with the form of my present invention therefore, coil ItY comprising a plurality of windings of extremely ne wire or other conductible material, is coiled `about a pair of identical end mountings broadly des. ignated by the numeral 30. Any suitable light. weight, butsturdy material may be used in makhighly important and to this extent it is seen portion 32 having a vsemi-circular, outermost face 34. It is upon these two faces 34 of elements 39-39 that theA coil I'I is wound in the manner illustrated by Figs. 2 and 3 of thedrawing. Coil I6 with its elements 30 is held in sus-I pension between vthe poles I4 by a pair of substantially identical ribbon-like-laments 36, the uppermost of which, as shown in Fig. l, carries the mirror 2li in any suitable fashion. The ribbons 36 are looped about the corresponding mounting element 3) in intersecting relationship or through the coil I8 and each bears against a fiat, innermost surface 38 on the corresponding mounting element 30.

In the modification chosen for illustration, the iiat surface 38 comprises the bottom wall of a notch 4I] that is formed in the semi-cylindrical portion 32 of each element 30 respectively. 1t is to @be understood however, that such notch 40 is provided solely to reduce the weight of the elements 30 and that the same may be eliminated if desired so long as a relatively flat, Vinner surface is presented for receiving filaments or looped` ribbons 3B. Accordingly, the fiat surfaces 38 against which the ribbons 35 bear, are substan-V tially parallel and appreciably wider than the Width of the ribbons 36 as is clear in Figs. 2

and 4.

The ends of the mounting elements 3B are de fined by a pair of spaced, semi-circular flanges 42 that extend laterally beyond the arcuate face 34 and terminate in a straight diametrical edge M aligned with Vthe innermost extremities of semicylindrical portion 32.

Fig. 3 of the drawing illustrates clearly the way in which the flanges i2 serve to embrace the coil a tendency to curl along the arcuate surface of a IE at its two ends to hold the same in place upon 1;.

the arcuate surfaces 3ft and also illustrates the way the ribbons 36 flatly engage the surfaces 38 throughout the bight thereof. From the inner faces 38, the legs of the ribbons extend outwardly beyond the coil i6 and bear flatly against the outer faces of the flanges l2 as is be positioned directly on the longitudinal axis of coil i6 or to one side thereof, will depend entirely upon the distribution of weight in the coil I6 and more particularly in the two elements 39.

It is virtually impossible to provide a pair of identical elements and therefore, irregular weight distribution may occur at any point to cause an unbalance in the vibratory assembly I8, either statically or dynamically w'hen the ribbons 3S are maintained in perfect alignment.

There are many methods of determining Ythe balance of coils of this character now employed in this field and otherwise available for use, one of which includes spinning of the assemblyV l 8 to determine the weight distribution thereof. Through use of such testing methods it is possible for the manufacturer to set the ribbons with respect to the surfaces 38 and to thereby attain absolutely perfect balance both statically and dynamically.

It is contemplated that after the ribbons 35 have been adjusted laterally with respect to the ing upon determination of the proper positioning thereof, theyfbe secured against Vmaladjustment with respect to the elements 30. The means of attachment of the ribbons 36 to the elements 30 forms no part of the present invention and .may, if desired, constitute a suitable adhesive `(not shown) joining the ribbons 3 to the sur- Amonly employed. Furthermore, the ribbons 3S cylindrical bore. Tests have proven that with a minimum amount of effort and time it is possible to provide galvanometers I0 having avibratory assembly I8 that is extremely sensitive to magnetic flux changes .between poles I4 when the assembly is made as herein provided.

In designing the vibratory assembly I8 the necessity for strength and rigidity has not been overlooked and while sensitivity has been increased tremendously to a point of virtual absolute perfection, the efficiency of the device from the standpoint of withstanding shock and other abuses, has not been depleted.

The degree of balance made possible by a galvanometer having a vibratory assembly made as above set forth becomes necessary because of new uses beingmade of instruments of this character in testing vibration, stress and strain in airborne frames and other industrialapplications vwhere the galvanometer is subjected to severe vibrations and yet must be extremely sensitive. Severe mechanical disturbances will not be refiected in rotary movement of the coil of the galvanometer forming the subject matter hereof and it will, thereby not be prevented from making a true record of any phenomena being photographed.

The importance of details of construction in a device of this character is now apparent but such changes and modifications as fairly come within the scope of the appended claims are manifestly contemplated hereby.

Having thus described the invention, what is claimed as new and desired to be secured by Letters Patent is: A g

1. In a vibratory assembly for galvanometers, a pair of spaced supports each having an arcuate outermost face and a flat innermost face; an elongated Vcoil wound about the supports and engaging the arcuate faces; and an elongated, fiat suspension ribbon looped about each support respectively through the coil in intersecting relationship thereto and in engagement with the flat faces, the width of said ribbons being less than the innermost width of the coil for rendering the ribbons shiftable with respect to the supports on the transverse axes of the ribbons and transversely of the longitudinal axis of the coil.

2. In a vibratory assembly for galvanometers as set forth in claim 1 wherein each support is provided with a notch, the said fiat innermost faces of the supports comprising the bottom wall of the notches.

3. In a vibratory assembly for galvanometers as set forth in claim 1 wherein the supports are each provided with a pair of spaced-apart flanges on the arcuate faces thereof for confining the coil therebetween.

MARVIN E. MORROW.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,519,591 Morrow Aug. 22, 1950 2,550,720 Richardson May 1, 1951 2,596,019 Fisher May 6, 1952 

